Screening for ratooning rice of direct seeding medium rice varieties suitable in Chongqing area and their high-yield abilities

【Objective】The objective of this study was to screen suitable rice varieties for ratooning rice of direct seeding medium rice in Chongqing and explore the characteristics of yield formation.The results could provide theoretical basis for ratooning rice of direct seeding production technology in Chongqing area.【Method】Fifteen good quality rice varieties of medium maturity and medium-late maturity, suitable for the upper reaches of Yangtze river were used as materials, ratooning rice was maintained from medium rice with mechanized wet seeding.Tested rice varieties were evaluated by using growth period, ratooning ability, break force, yield and yield components and other indicators.【Result】Results indicated that variety had significant difference on growth period, ratooning ability, break force, yield and yield components of medium rice and ratoon rice(P< 0.05, the same below).Under direct seeding condition, the whole growth periods were from 201 to 217 d, and the ratooning abilities were from 0.75 to 1.36, and the break forces were from 0.89 to 1.57 kg, and the medium rice yields were from 6.29 to 9.90 t/ha, and the ratooning rice yields were from 2.84 to 4.71 t/ha, and the total yield of two seasons were from 9.81 to 12.80 t/ha.According to the cluster analysis based on grain yield, there were five rice types among the 15 tested varieties, including HMHR(high-yield medium rice and high-yield ratooning rice), HMMR(high-yield medium rice and middle-yield ratooning rice), MMMR(middle-yield medium rice and middle-yield ratooning rice), LMHR(low-yield medium rice and high-yield ratooning rice) and LMMR(low-yield medium rice and high-yield ratooning rice).The selected HMHR type and HMMR type, including Chuanyou 5213, Chuanyou 8213, Xiyou 32, Chuankangyou 637, Jing 22 youzhan, B you 2928 and Chuanlüyouqingzhan were suitable for ratooning rice of direct seeding medium rice.The correlation analysis showed that the yield of medium rice had significant positive correlation with the whole growth period, extremely significant positive correlation with the growth period of ratooning rice(P< 0.01, the same below), extremely significant positive correlation with the seed-setting rate of medium rice, significant positive correlation with 1000-grain weight of medium rice.The yield of ratooning rice had significant positive correlation with grains per panicle and effective panicles, extremely significant positive correlation with the ratooning ability.The total yield of two seasons had extremely significant positive correlation with the yield of medium rice and the seed-setting rate.【Conclusion】Seven rice varieties such as Chuanyou 5213 are suitable for ratooning rice of direct seeding medium rice.These can be applied in breeding of the suitable rice varieties for ratooning rice of direct seeding medium rice and improvement of rice landraces in Chongqing area.